The manufacture of integrated-circuit devices such as, e.g., semiconductor memory and logic chips involves numerous processing steps including ion implantation, deposition of dielectric and conductor layers on a wafer substrate, and photolithographic patterning and etching. More particularly with respect to the deposition of conductor layers on a dielectric, such layers may be formed, e.g., by (physical) sputtering, evaporation, or by chemical vapor deposition (CVD). Prominent in current use are sputtering for aluminum, and chemical vapor deposition for tungsten.
One difficulty encountered especially with respect to conductor metallization layers arises with unsatisfactory adhesion of metallization material to the dielectric, making it advisable, prior to metal deposition, to form an auxiliary, adhesion-enhancing "glue" layer. Since such glue layer is typically deposited by sputtering onto the face of a wafer while the wafer is held by clips, the wafer back side, the wafer edge, and small areas of the wafer face underlying the clips ("clip marks") remain essentially as uncoated dielectric. As a result, subsequently deposited metallization material tends to flake off from such uncoated areas in the course of further processing, thereby contaminating processing apparatus and interfering with desired processing.
The invention described below is motivated by the desire to prevent metal flake-off and attendant contamination and interference.